I recently listened to a talk given by Brian Lunduke about problems that GNU/Linux are currently facing. In it (roughly 26m48s into the video) he mentions that keynote presentation time slots are being purchased by companies at GNU/Linux conferences. That is, companies are paying the conferences in order to get to be keynote speakers at said conferences.
This made me think, does this kind of thing happen in the academic world too? Are there serious conferences (that is, not the type of conferences we so often get spam emails about) where some or all of the keynote talks have been chosen due to some company/organisation/person paying the conference money in order to get their person to speak there? If so, is this disclosed to the conference participants in any reasonable way?